Inter-Frame Spacing Duration for Sub-1 Gigahertz Wireless Networks

ABSTRACT

Systems and methods of performing communication via a sub-1 gigahertz wireless network are disclosed. Values of one or more inter-frame spacing parameters for use in communication via the sub-1 gigahertz wireless network are also defined. The parameters may include a short inter-frame spacing (SIFS) time of 160 microseconds (μs). The parameters may also include a clear channel assessment (CCA) time of 40 μs. Additional parameters, such as air propagation time are also defined (e.g., for inclusion into a standard, such as Institute of Electrical and Electronics Engineers (IEEE) 802.11ah).

I. CLAIM OF PRIORITY

This application claims priority from U.S. Provisional PatentApplication No. 61/658,341, filed Jun. 11, 2012, entitled “INTERFRAMESPACING DURATION FOR IEEE 802.11AH,” U.S. Provisional Patent ApplicationNo. 61/669,489, filed Jul. 9, 2012, entitled “INTERFRAME SPACINGDURATION FOR IEEE 802.11AH,” and U.S. Provisional Patent Application No.61/677,336, filed Jul. 30, 2012, entitled “INTERFRAME SPACING DURATIONFOR IEEE 802.11AH,” the contents of each of which are incorporated byreference in their entirety.

II. FIELD OF THE DISCLOSURE

The present disclosure is generally directed to inter-frame spacingduration for sub-1 gigahertz wireless networks.

III. BACKGROUND

Advances in technology have resulted in smaller and more powerfulcomputing devices. For example, there currently exist a variety ofportable personal computing devices, including wireless computingdevices, such as portable wireless telephones, personal digitalassistants (PDAs), and paging devices that are small, lightweight, andeasily carried by users. More specifically, portable wirelesstelephones, such as cellular telephones and Internet Protocol (IP)telephones, can communicate voice and data packets over wirelessnetworks. Further, many such wireless computing devices include othertypes of devices that are incorporated therein. For example, wirelesscomputing devices can also include a digital still camera, a digitalvideo camera, a digital recorder, and an audio file player. Also, suchwireless computing devices include a processor that can processexecutable instructions, including software applications, such as a webbrowser application, that can be used to access the Internet. As such,these wireless computing devices can include significant computingcapabilities. As use of wireless computing devices increases, bandwidthallocated to wireless communication may become congested with increasedtraffic. To alleviate such congestion, one possible approach is toallocate bandwidth to wireless computing devices that was previouslyunderutilized.

As demand for wireless data communications has increased, communicationsystems may be designed to operate in the underutilized sub-1 GHz(gigahertz) spectrum in the Industrial, Scientific, and Medical (ISM)band. In addition to use of the underutilized sub-1 GHz spectrum,improved coverage range of the communication systems may allow newapplications to emerge, such as wide area based sensor networks, sensorbackhaul systems, and wireless fidelity (Wi-Fi) off-loading functions.

IV. SUMMARY

The Institute of Electrical and Electronics Engineers (IEEE) haspromulgated various industry specifications related to wirelessnetworking, many of which are designated with the “IEEE 802.11” name.For example, 802.11b (entitled “Higher Speed Physical Layer Extension inthe 2.4 GHz Band” and referred to as Clause 18) is a wireless networkingstandard that may be used in customer premise wireless networking, suchas in a home or office environment and 802.11n (entitled “Standard forInformation Technology—Local and Metropolitan Area Networks—SpecificRequirements Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications Amendment 5: Enhancements for HigherThroughput 2009”) is a wireless networking standard that may be used forhigh speed wireless local area network (WLAN) implementations. “Inprogress” IEEE 802.11 standards include 802.11ac (entitled “Enhancementsfor Very High Throughput”) and 802.11ah (entitled “Sub-1 GHz SensorNetwork”). IEEE 802.11ah is a standard for using carrier frequenciesbelow 1 GHz in the Industrial, Scientific, and Medical (ISM) band forwireless local area network (WLAN) communication. Some items not yetfinalized by IEEE 802.11ah include physical layer (PHY) parameters orconstraints.

The present disclosure provides one or more parameters or constraintsfor sub-1 GHz networks (e.g., networks that may be compatible with theIEEE 802.11ah standard) and for transmissions (e.g., transmissions thatcomply with the IEEE 802.11ah standard) to enable a station (e.g., atransmitter or a transmit station) to transmit a protocol data unit(PPDU). The one or more parameters or constraints may be associated withor include one or more inter-frame spacing (timing) parameters. Inparticular embodiments, the selected inter-frame spacing values may bethe minimum required to achieve successful operation for a carrier sensemultiple access (CSMA) mechanism in IEEE 802.11ah systems.

Based on the one or more parameters or constraints, a station (e.g., amobile communication device) may transmit a PPDU using bandwidthchannels with carrier frequencies below 1 GHz in the Industrial,Scientific, and Medical (ISM) band. The PPDU may include one or moresymbols and may be transmitted via a wireless local area network (WLAN).The channels may include 1 megahertz (MHz) bandwidth channels, 2 MHzbandwidth channels, 4 MHz bandwidth channels, 8 MHz bandwidth channels,16 MHz bandwidth channels, or a combination thereof. For example, in theUnited States, twenty-six 1 MHz bandwidth channels, thirteen 2 MHzbandwidth channels, six 4 MHz bandwidth channels, three 8 MHz bandwidthchannels, or one 16 MHz bandwidth channel of the 902 MHz-928 MHzwireless spectrum may be used. The lower half of each 2 MHz bandwidthchannel may be used as a primary 1 MHz bandwidth channel and the upperhalf of each 2 MHz bandwidth channel may be used as a secondary 1 MHzbandwidth channel. For example, a station may use the primary bandwidthchannel to transmit data having 1 MHz bandwidth and may use both theprimary bandwidth channel and the secondary channel to transmit datahaving 2 MHz bandwidth. A station using a 1 MHz bandwidth channel may besaid to be operating in a 1 MHz mode. A station using a 2 MHz bandwidthchannel may be said to be operating in a 2 MHz mode.

In a particular embodiment, an apparatus includes a transmitter. Thetransmitter is operable to transmit a frame, via a sub-1 gigahertz (GHz)wireless network, at a start time based at least in part on a shortinter-frame spacing (SIFS) time of 160 microseconds.

In another particular embodiment, a non-transitory computer-readablestorage device stores instructions. The instructions, when executed by aprocessor, cause the processor to initiate transmission, via a sub-1gigahertz (GHz) wireless network, of a frame at a start time based on ashort inter-frame spacing (SIFS) time. The SIFS time is 160microseconds.

In another particular embodiment, a non-transitory computer-readablestorage device stores instructions. The instructions, when executed by aprocessor, cause the processor to initiate transmit, via a sub-1gigahertz (GHz) wireless network, of a frame at a start time based on aclear channel assessment (CCA) time. The CCA time is 40 microseconds.

In another particular embodiment, a method includes transmitting, from astation, a frame via a sub-1 gigahertz (GHz) wireless network. The frameis transmitted at a start time based at least in part on a clear channelassessment (CCA) time of 40 microseconds.

An advantage provided by the disclosed embodiments is one or moreinter-frame spacing parameters that enable transmission and reception ofdata via a sub-1 GHz wireless network. The one or more inter-framespacing parameters may be included in a standard, such as the IEEE802.11ah standard.

Other aspects, advantages, and features of the present disclosure willbecome apparent after review of the application, including the followingsections: Brief Description of the Drawings, Detailed Description, andthe Claims.

V. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an illustrative embodiment of a system thatcommunicates data via a sub-1 GHz wireless network;

FIG. 2 is a timing diagram of associated with transmission of a framebased on one or more inter-frame spacing parameters associated withsub-1 GHz wireless networks;

FIG. 3 is a flow diagram illustrating a particular method oftransmitting a frame via a sub-1 GHz wireless network, the transmissionbased on one or more inter-frame spacing parameters; and

FIG. 4 is a block diagram of a particular embodiment of a device that isconfigured to communicate data over a sub-1 GHz wireless network.

VI. DETAILED DESCRIPTION

Particular embodiments of the present disclosure are described belowwith reference to the drawings. In the description, common features aredesignated by common reference numbers throughout the drawings.

A station may transmit a data packet (e.g., including a data symbol or aPPDU) via a sub-1 GHz network. Transmission of the data packet may bebased on one or more inter-frame spacing (timing) parameters. Forexample, the one or more parameters or constraints may be included in anInstitute of Electrical and Electronics Engineers (IEEE) 802.11 ahstandard.

FIG. 1 is a diagram of a particular embodiment of a system 100 that isoperable to communicate data via a wireless network 140. The system 100includes a transmitter station 106 and a receiver station 160. Thetransmitter station 106 may be configured to transmit a packet 130 tothe receiver station 160 via the network 140. Although a singletransmitter and a single receiver are shown in FIG. 1, alternateembodiments include more than one transmitter, more than one receiver,or both. Although a dedicated transmitter station 106 and a dedicatedreceiver station 160 are shown in FIG. 1, some devices may be capable ofboth packet transmission as well as packet reception (e.g., transceiversor mobile communication devices that include a transceiver). Thus, thenetwork 140 supports two-way communication.

The network 140 may operate in accordance with an IEEE 802.11ahprotocol. The network 140 may support communication via a plurality ofchannels (e.g., sub-1 GHz bandwidth channels). In a particularembodiment, a bandwidth of channels of the network 140 varies from 1 MHzto 16 MHz, depending on regulatory guidelines in a geographic regionwhere the network 140 is located. For example, a channel bandwidth maybe 16 MHz in the United States, 2 MHz in Europe, and 4 MHz in anotherregulatory domain. When data is communicated via the network 140,operating bandwidth used for communication in each of the channels maybe less than or equal to the channel bandwidth of the channel. Forexample, operating bandwidth within a 2 MHz channel (e.g., in the UnitedStates) may be 1.5 MHz, 1.66 MHz, 1.75 MHz, 2 MHz, or some otherbandwidth less than or equal to 2 MHz.

The transmitter station 106 may include a processor 108, a memory 110, apacket creation/encoding module 114, a baseband processor 116, and atransmitter 118. The processor 108 (e.g., a digital signal processor(DSP), an application processor, etc.) may be coupled to the memory 110.In a particular embodiment, the processor 108 includes logic (e.g.,hardware and/or circuit elements) to generate the packet 130 to betransmitted via the network 140. Alternatively, the packet 130 may begenerated, encoded, or a combination thereof, by the packetcreation/encoding module 114 (e.g., hardware, circuit elements,software, or a combination thereof).

The memory 110 may be a non-transitory computer readable storage mediumthat stores data, instructions, or both. The memory 110 may include PHYparameters 112 associated with the network 140 and with transmission ofthe packet 130. The transmitter station 106 may transmit the packet 130(e.g., a protocol data unit (PPDU) or a data symbol) via the network 140based on the PHY parameters 112. For example, the PHY parameters 112 maybe associated with one or more inter-frame spacing (timing) parameters.In a particular embodiment, the PHY parameters 112 are stored in a tableor an array in the memory 110, hardcoded in one or more circuits orcomponents, or a combination thereof.

The memory 110 may also include instructions (not shown) that areexecutable by the processor 108 to cause the processor 108 to performone or more functions or methods as further described herein. Forexample, the instructions may include or represent user applications, anoperating system, other executable instructions, or a combinationthereof. Further, the memory 110 may store the packet 130 generated bythe processor 108 or generated by the packet creation/encoding module114.

The baseband processor 116 (e.g., an IEEE 802.11ah baseband processor)may be coupled to the processor 108, the packet creation/encoding module114, and the transmitter 118. The baseband processor 116 may include aclock 104. The transmitter 118 may include filter(s) 102 (e.g., one ormore radio frequency (RF) filters), a media access control (MAC) module152, and a physical layer convergence procedure (PLCP) module 154. Thetransmitter 118 may include a transceiver that enables the transmitterstation 106 to wirelessly transmit data and wirelessly receive data. Thetransmitter 118 (e.g., a RF transmitter) may be coupled to one or morewireless antennas 120. Additionally, the transmitter station 106 mayinclude one or more oscillators for use in generating a transmit centerfrequency, a symbol clock frequency, or a combination thereof, for useby the transmitter station 106. In a particular embodiment, theprocessor 108 may initiate sending of the packet 130 (via the basebandprocessor 116, the transmitter 118, and the wireless antennas 120) fromthe transmitter station 106 to the receiver station 160 or anotherdevice via one or more channels of the network 140. Transmission of thepacket 130 via the network 140 may comply with one or more constraintsincluded in the IEEE 802.11ah standard. For example, the transmitterstation 106 may transmit the packet 130 based on inter-frame spacingparameters specified by the IEEE 802.11ah standard.

The receiver station 160 may include a station, an access point, oranother device configured to receive one or more data packets (e.g.,data symbols), such as the packet 130 sent via the network 140. Thereceiver station 160 may include a processor 168, a memory 170, a packetdecoding module 174, a baseband processor 176, and a receiver 178. Theprocessor 168 (e.g., a digital signal processor (DSP), an applicationprocessor, etc.) may be coupled to the memory 170. In a particularembodiment, the processor 168 includes logic (e.g., hardware and/orcircuit elements) to process the packet 130 received at the receiverstation 160 via the network 140. Alternatively, the packet 130 may bedecoded (e.g., deconstructed) by the packet decoding module 174 (e.g.,hardware, circuit elements, software, or a combination thereof).

The memory 170 may be a non-transitory computer readable storage mediumthat stores data, instructions, or both. The memory 170 may include PHYparameters 172 associated with the network 140 and reception oftransmission of the packet 130. The receiver station 160 may receive thepacket 130 (e.g., a protocol data unit (PPDU) or a data symbol) via thenetwork 140 and process the received packet 130 based on the PHYparameters 172. For example, the PHY parameters 172 may be associatedwith one or more inter-frame spacing (timing) parameters. In aparticular embodiment, the PHY parameters 172 are stored in a table oran array in the memory 170, hardcoded in one or more circuits orcomponents, or a combination thereof.

The memory 170 may also include instructions (not shown) that areexecutable by the processor 168 to cause the processor 168 to performone or more functions or methods as further described herein. Forexample, the instructions may include or represent user applications, anoperating system, other executable instructions, or a combinationthereof. Further, the memory 170 may store the packet 130 or processeddata from the packet 130 generated by the processor 108 or the packetdecoding module 174.

The baseband processor 176 (e.g., an IEEE 802.11ah baseband processor)may be coupled to the processor 168, the packet decoding module 174, andthe receiver 178. The baseband processor 176 may include a clock 164.The receiver 178 may include filter(s) 162 (e.g., one or more RFfilters), a media access control (MAC) module 192, and a physical layerconvergence procedure (PLCP) module 194. The receiver 178 may include atransceiver that enables the receiver station 160 to wirelessly transmitdata and wirelessly receive data. The receiver 178 (e.g., a RF receiver)may be coupled to one or more wireless antennas 180. Additionally, thereceiver station 160 may include one or more oscillators for use ingenerating one or more clock signals or frequency signals. In aparticular embodiment, the receiver station 160 may receive the packet130 (via the wireless antennas 180, the receiver 178, and the basebandprocessor 176) from the transmitter station 106 or another device viaone or more channels of the network 140. Transmission and reception ofthe packet 130 via the network 140 may comply with one or moreconstraints included in the IEEE 802.11ah standard.

During operation, the processor 108, the packet creation/encoding module114, the baseband processor 116, or a combination thereof, of thetransmitter station 106 may create (e.g., generate) and encode thepacket 130 based on the PHY parameters 112. The packet 130 may betransmitted by the transmitter station 106 via the transmitter 118 andthe one or more wireless antennas 120. The packet 130 may be transmittedto the receiver station 160 via the network 140. Transmission of thepacket 130 via the network 140 may comply with one or more constraintsincluded in the IEEE 802.11ah standard. The receiver station 160 mayreceive the packet 130 via the one or more wireless antennas 180 and thereceiver 178. The processor 168, the packet decoding module 174, thebaseband processor 176, or a combination thereof, may decode the packet130 based on the PHY parameters 172.

The system 100 may thus provide a transmitter configured to transmit adata packet (e.g., a data symbol or PPDU) via a sub-1 GHz bandwidthchannel of the network 140 and a receiver to receive the data packet.The packet 130 may conform to and comply with one or more standards,such as the IEEE 802.11ah standard. For example, the IEEE 802.11ahstandard may include one or more inter-frame spacing parameters, asfurther described herein.

Inter-Frame Spacing (Timing) Parameters

Inter-frame spacing (e.g., a spacing value between two frames)parameters may include a clear channel assessment (CCA) time, a CCA midtime, an air propagation time, a slot time, and a short inter-framespace (SIFS) period. Exemplary values that may be used for the one ormore parameters are provided in TABLE 1—Inter-frame Spacing Parameters.In TABLE 1, the exemplary values are in units of microseconds (μs).

TABLE 1 Inter-frame Spacing Parameters CCA Time 40 μs CCA Mid Time 25 μsAir Propagation Time 6 μs Slot Time 52 μs SIFS 16 μs

The slot time and the SIFS time may be calculated based in part onexemplary timing intervals as shown in FIG. 2. Referring to FIG. 2, atiming diagram 200 associated with transmission of a frame (e.g.,including a PPDU, a data symbol, the packet 130, or a combinationthereof) based on one or more inter-frame spacing parameters associatedwith a network (e.g., the network 140 of FIG. 1) is shown. One or moreaspects of the timing diagram 200 are based on one or more PHYparameters or constraints, such as the PHY parameters 112, 172 ofFIG. 1. For example, FIG. 2 defines various timing periods associatedwith carrier sense multiple access (CSMA) communication. Based on thetiming diagram 200, transmission of a frame (e.g., including a PPDU, adata symbol, or a combination thereof) of a transmitted packet iscontrolled based on timing parameters including a distributedcoordination function (DCF) inter-frame spacing (DIFS) period and afirst backoff slot period. The DIFS period includes a time durationduring which the transmission station 106 determines that a medium iscontinuously idle before starting transmission of the frame. If thetransmission station 106 determines that the medium is not continuouslyidle during the DIFS period, the transmission station 106 continues tomonitor a busy or idle status of the medium. After determining that themedium is idle for a DIFS period, the transmission station 106 deferstransmission of the frame for the first backoff slot period. The DIFSperiod includes a sum of a SIFS period and twice a slot time period. Anaccess point (e.g., the transmitter station 106) may determine that themedium is continuously idle for a point coordination function (PCF)inter-frame spacing (PIFS) period, instead of the DIFS period, beforetransmitting the frame. The PIFS period includes a sum of the SIFSperiod and the slot time period. The PIFS period is shorter than theDIFS period, giving the access point greater priority to transmit thanother devices.

The SIFS period includes a time duration between receiving a frame andsending an acknowledgement (ACK). For example, the receiver station 160may receive the frame and wait for the SIFS period before sending anACK. The SIFS period includes processing and turnaround delays. Forexample, the SIFS period includes a receive (Rx) radio frequency (RF)delay, a RX physical layer convergence procedure (PLCP) delay, a mediaaccess control (MAC) processing delay, and a Rx transmit (Tx) turnaroundtime. The Rx Tx turnaround time includes a Tx PLCP delay, a Rx Tx switchtime, a Tx ramp-on time, and a Tx RF delay.

The slot time includes processing, turnaround, and air propagation time.For example, the slot time includes an air propagation time, the MACprocessing delay, and the RxTx turnaround time. IEEE 802.11ah mayspecify a maximum distance between any two stations (i.e., the mostdistant allowable stations) that are slot synchronized. The airpropagation time (indicated in microseconds in TABLE 1) is twice anamount of time (i.e., round trip propagation time) for a signal to crossa distance between the most distant allowable stations that are slotsynchronized. The slot time also includes a clear channel assessment(CCA) time.

The CCA time includes a time duration (indicated in microseconds inTABLE 1) that a CCA mechanism of the transmitter station 106 has accessto the medium within each time slot to determine whether the medium isbusy or idle. In a particular embodiment, the CCA time may correspond toa time duration that the transmitter station 106 has access to a primarybandwidth channel within each time slot to determine whether the primarybandwidth channel is busy or idle. In this embodiment, the CCA mid timeincludes a time duration (indicated in microseconds in TABLE 1) that theCCA mechanism of the transmitter station 106 has access to the secondarybandwidth channel within each time slot to determine whether thesecondary bandwidth channel is busy or idle.

In a particular embodiment, the transmitter station 106 may transmit adata symbol based on one or more inter-frame timing parameters, wherethe data symbol is transmitted via one or more bandwidth channels (e.g.,a primary bandwidth channel or the primary bandwidth channel and asecondary bandwidth channel).

Inter-frame spacing (e.g., a spacing value between two frames) may bebased on a parameter combination including a SIFS time of 160microseconds, a slot time of 52 microseconds, a CCA time of 40microseconds, a CCA mid time of 250, an air propagation time of 6microseconds, or a combination thereof.

In a particular embodiment, the SIFS time, the slot time, or both, maybe received by a station (e.g., the transmitter station 106, thereceiver station 160), may be preset, may be determined by the stationand stored in memory, or a combination thereof.

The SIFS time and the slot time may be calculated based on exemplarytiming intervals as shown in FIG. 2. For example, the SIFS time may be asum of D1, M1, and Rx/Tx of FIG. 2, where D1 represents a Rx RF delay,M1 represents a MAC processing delay, and Rx/Tx represents a Rx/Txturnaround time. As another example, the slot time may be a sum of D2,CCAdel, M2, and Rx/Tx of FIG. 2, where D2 represents a sum of D1 and airpropagation time, CCAdel represents a difference between a CCA time andD1, and M2 represents a MAC processing delay. Thus, the slot time may bea sum of the air propagation time, the CCA time, the MAC processingdelay, and the Rx/Tx turnaround time. The Rx/Tx turnaround time may be asum of a Tx PLCP delay, a Rx/Tx switch time, a Tx ramp on time, and a TxRF delay.

The SIFS time and the slot time may be calculated based on one or morevalues and assumptions, such as one or more values and assumptionsassociated with an air propagation time, a Rx PLCP delay, a MACProcessing delay, a Tx PLCP delay, a Tx ramp on time, an Rx/Tx switchtime, a Tx RF delay, an Rx RF delay, or a CCA time.

Exemplary values of inter-frame spacing parameter combinations areprovided with reference to TABLES 2 and 3.

TABLE 2 SIFS aRxRFDelay 5 μs aRxPLCPDelay 125 μs aMACProcessingDelay 10μs aRxTxTurnaroundTime 15.5 (10 + 0.25 + (aTxPLCPDelay +aRxTxSwitchTime + 0.25 + 5) μs aTxRampOnTime + aTxRFDelay) SIFS 156 μsSIFS (multiple of 40 μs) 160 μs

TABLE 3 SLOT TIME CCA Time 40 μs Air Propagation Time 6 μsaMACProcessingDelay 0 μs aRxTxTurnaroundTime 5.5 (0 + 0.25 +(aTxPLCPDelay + aRxTxSwitchTime + 0.25 + 5) μs aTxRampOnTime +aTxRFDelay) Slot Time 52 μs

In a particular embodiment, IEEE 802.11ah may specify a maximum distanceof 900 meters between any two stations (i.e., the most distant allowablestations) that are slot synchronized. Assuming that a signal propagatesat approximately 300 meters per microsecond, the air propagation time inthis embodiment may be about 6 microseconds (i.e., 2*(900 meters/300meters per microsecond)).

The Rx PLCP delay (aRxPLCPDelay), the MAC processing delay(aMACProcessingDelay), and the Tx PLCP delay (aTxPLCPDelay) includedigital processing delays that may depend on a first digital clock rateassociated with a baseband processor (e.g., an IEEE 802.11ah basebandprocessor, such as the baseband processor 116 of FIG. 1 or the basebandprocessor 176 of FIG. 1). The Rx PLCP delay is a time duration that aPLCP module (e.g., the PLCP module 194) may take to deliver a last bitof a received frame from a receive path to a MAC module (e.g., the MACmodule 192). The Tx PLCP delay is a time duration that a PLCP module(e.g., the PLCP module 154) may take to deliver a symbol from a MACmodule (e.g., the MAC module 152) to a transmit data path. The MACprocessing delay may represent a processing delay of a MAC module. Forexample, the MAC processing delay is a maximum duration that a MACmodule (e.g., the MAC module 152, the MAC module 192, or both) may taketo process communications to and from the PLCP module (e.g., the PLCPmodule 154, the PLCP module 194, or both).

The first digital clock rate (e.g., as specified by the IEEE 802.11ahstandard) may be equivalent to a second digital clock rate (e.g.,associated with an IEEE 802.11n/ac baseband processor) downclocked by aparticular factor (e.g., 10). The digital processing delays (e.g., theaRxPLCPDelay, aMACProcessingDelay, and aTxPLCPDelay values) associatedwith the first digital clock rate may be determined by multiplying thedigital processing delays associated with the second digital clock rateby the downclocking factor (i.e., 10). In a particular embodiment,aRxPLCPDelay associated with the second digital clock rate may be 12.5microseconds and aMACProcessingDelay and aTxPLCPDelay associated withthe second digital clock rate may be 1 microsecond each. In thisembodiment, the aRxPLCPDelay associated with the first digital clockrate may be 125 microseconds (i.e., 12.5×10) and aMACProcessingDelay andaTxPLCPDelay associated with the first digital clock rate may be 10microseconds (i.e., 1×10) each.

TABLE 3 includes exemplary values that may be used to determine the slottime. The slot time may be determined based on aMACProcessingDelay ofzero, because the MAC calculation may be done by the transmitter station106 prior to (e.g., before) a transmission. The slot time may bedetermined based on aTxPLCPDelay of zero.

The Tx ramp on time (aTxRampOnTime) and the Rx Tx switch time(aRxTxSwitchTime) may be assumed to be the same as specified by IEEE802.11n/ac. The Tx RF delay (aTxRFDelay) and the Rx RF delay(aRxRFDelay), assuming a same filter order as specified by IEEE802.11n/ac, may increase due to bandwidth scaling (e.g., 10× based on 2MHz IEEE 802.11ah bandwidth vs. 20 MHz IEEE 802.11n/ac bandwidth) ascompared to IEEE 802.11n/ac. Furthermore, a station operating in the 1MHz mode may use the same filter (e.g., the filter(s) 102 or thefilter(s) 162) as when operating in the 2 MHz mode. If a narrower filteris used in the 1 MHz mode, a longer filter delay associated with usingthe narrower filter may be compensated by a smaller digital delay of the1 MHz mode.

The CCA time and the CCA mid time may depend on the first digital clockrate associated with the baseband processor (e.g., the IEEE 802.11ahbaseband processor). Based on a downclocking factor of 10, the CCA timeand the CCA mid time specified by IEEE 802.11n/ac may be multiplied by10. For example, the CCA time may be 40 microseconds (i.e., 4×10) andthe CCA mid time may be 250 microseconds (i.e., 25×10). The CCA time of40 microseconds may be long enough to achieve a greater than 90%detection rate of a presence of a signal that occupies the primarybandwidth channel. The CCA mid time of 250 microseconds may be longenough to achieve a greater than 90% detection rate of a presence of asignal that occupies the secondary bandwidth channel.

As illustrated in TABLE 2, the SIFS time may be a multiple of symboltime (e.g., 40 microseconds) that is close to the exemplary SIFS timecalculated based on the downclocking factor. For example, the SIFS timemay be 160 microseconds instead of the SIFS time of 156 microseconds.

The system 100 may thus include a transmitter configured to transmit adata packet (e.g., a data symbol or PPDU) via a sub-1 GHz bandwidthchannel of the network 140 and a receiver to receive the data packet.The packet may conform to and comply with one or more standards, such asthe IEEE 802.11ah standard. For example, the IEEE 802.11ah standard mayspecify one or more inter-frame spacing parameters, as further describedherein.

Wireless local area networks (WLANs) compliant with the IEEE 802.11acstandard may operate in high frequency bands (e.g., 5 GHz) and mayprovide data rates ranging to more than 1 gigabit per second (Gbps).However, the range of operation of WLANs compliant with the IEEE 802.11ac standard may be relatively short due to high frequency of operation.The range of operation may be extended by lowering operatingfrequencies. However, lower operating frequencies may result in lowerdata rates. For example, WLANs compliant with the IEEE 802.11ah standardmay operate in a sub-1 GHz frequency band and may have a longer range ofoperation but may also have lower data rates than the WLANs compliantwith the IEEE 802.11ac standard. A slower clock rate may support alonger range of operation and may also support communication usingnarrower bandwidth channels. For example, a first clock rate associatedwith the IEEE 802.11ah standard may be slower than a second clock rateassociated with the IEEE 802.11ac standard. The slower clock rateassociated with the IEEE 802.11ah standard may support the longer rangeof operation of WLANs compliant with the IEEE 802.11ah standard ascompared to WLANs compliant with the IEEE 802.11ac standard. The slowerclock rate may also support communication using narrower bandwidthchannels in the WLANs compliant with the 802.11ah standard as comparedto the WLANs compliant with the 802.11ac standard.

Referring to FIG. 3, a particular illustrative embodiment of a method oftransmitting a frame via a sub-1 gigahertz wireless network is shown.For example, the frame may include the packet 130 of FIG. 1.

The method 300 may include generating a frame at a station, at 302. Forexample, the station may include the transmitter station 106 of FIG. 1and the frame may include the packet 130 of FIG. 1. To illustrate, thetransmitter station 106 may transmit the packet 130 via the network 140,where the packet 130 is transmitted at a start time that is determinedbased on the PHY parameters 112.

The method 300 may also include transmitting, from the station, theframe via a sub-1 GHz wireless network, at 304. The frame may betransmitted at a start time.

For example, at 306, the start time may be based at least in part on ashort inter-frame space (SIFS) time of approximately 160 microseconds.

As another example, at 308, the start time may be based at least in parton a slot time of approximately 52 microseconds.

As another example, at 310, the start time may be based at least in parton a clear channel assessment (CCA) time of approximately 40microseconds.

As another example, at 312, the start time may be based at least in parton a CCA mid time of approximately 250 microseconds.

As another example, at 314, the start time may be based at least in parton an air propagation time of approximately 6 microseconds.

In a particular embodiment, the method 300 may include one or more of306-314. For example, the start time may be based at least in part onthe SIFS time of approximately 160 microseconds, at 306, the slot timeof approximately 52 microseconds, at 308, the CCA time of approximately40 microseconds, at 310, the CCA mid time of approximately 250microseconds, at 312, the air propagation time of approximately 6microseconds, at 314, or a combination thereof.

FIG. 4 is a block diagram of a particular embodiment of a device 400(e.g., a communication device) configured to transmit or receive datausing a sub-1 GHz network. The device 400 may be a wireless electronicdevice and may include a processor 410, such as a digital signalprocessor (DSP), coupled to a memory 432. For example, the device 400may include the transmitter station 106 of FIG. 1, the receiver station160 of FIG. 1, or both. The memory 432 may include the memory 110 ofFIG. 1, the memory 170 of FIG. 1, or both.

The processor 410 may be configured to execute software 466 (e.g., aprogram of one or more instructions) stored in the memory 432. Forexample, the processor 410 may include the processor 108 of FIG. 1, theprocessor 168 of FIG. 1, or both. In a particular embodiment, theprocessor 410 may be configured to operate in accordance with at least aportion of the method 300 of FIG. 3. The memory 432 may also include PHYparameters 468. For example, the PHY parameters 468 may include the PHYparameters 112 of FIG. 1, the PHY parameters 172 of FIG. 1, or both. ThePHY parameters 468 may include one or more parameter values illustratedin TABLES 1-3. One or more of PHY parameters 468 may be used by thedevice 400 in conjunction with transmission or reception of one or moredata packets (e.g., one or more data symbols).

In a particular embodiment, the processor 410 may be configured toexecute computer executable instructions (e.g., the software 466) storedat a non-transitory computer-readable medium, such as the memory 432.The instructions are executable to cause a computer, such as theprocessor 410, to perform at least a portion of the method 300 of FIG.3. For example, the computer executable instructions may be executableto cause the processor generate or process a data packet (e.g., a PPDU,a data symbol, a frame, or the packet 130 of FIG. 1). The computerexecutable instructions (e.g., the software 466) are further executableto cause the processor 410 to initiate transmission of or to receive thedata packet via a sub-1 GHz bandwidth channel (e.g., of the network 140of FIG. 1).

The processor 410 may include an encoder 452 and a decoder 454. Forexample, the encoder 452 and the decoder 454 may include the packetcreation encoding module 114 and the packet decoding module 174 of FIG.1, respectively. Although the encoder 452 and the decoder 454 areillustrated in FIG. 4 as being included in the processor 410, theencoder 452, the decoder 454, or a combination thereof, may be includedin or coupled to one or more other components, such as one or morebaseband processors 480, of the device 400.

In a particular embodiment, the baseband processors 480 may include afirst baseband processor that is configured to operate in compliancewith the IEEE 802.11ah standard. For example, the baseband processors480 may include the baseband processor 116 of FIG. 1, the basebandprocessor 176 of FIG. 1, or both. In a particular embodiment, thebaseband processors 480 may include a second baseband processor that isconfigured to operate in compliance with another standard (e.g., theIEEE 802.11n/ac standard). One or more inter-frame spacing parametersmay be determined based at least in part on digital processing delays(e.g., an Rx PLCP delay, a MAC processing delay, a Tx PLCP delay, or acombination thereof). The digital processing delays may be based on aclock rate. In a particular embodiment, a first clock rate associatedwith the first baseband processor may be equivalent to a second clockrate associated with the second baseband processor downclocked by aparticular factor (e.g., 10). In this embodiment, a first digitalprocessing delay (e.g., an Rx PLCP delay) associated with the IEEE802.11ah standard may be determined by multiplying a second digitalprocessing delay (e.g., an Rx PLCP delay of 12.5 microseconds)associated with the IEEE 802.11n/ac standard by the downclocking factor(i.e., 10). The baseband processors 480 may be included in or coupled toone or more components of the device 400, such as the processor 410, theencoder 452, the decoder 454, a transmitter 440, a receiver 446, or acoder/decoder (CODEC) 434.

A camera interface 496 may be coupled to the processor 410 and may alsobe coupled to a camera, such as a video camera 498. A display controller426 may be coupled to the processor 410 and to a display device 428. TheCODEC 434 may also be coupled to the processor 410. A speaker 436 and amicrophone 438 may be coupled to the CODEC 434. The device 400 may alsoinclude or be coupled to a power supply 444 configured to provide powerto one or more components included in or coupled to the device 400.

The transmitter 440 may be coupled to one or more wireless antennas 442.For example, the wireless antennas 442 may include the wireless antennas120 of FIG. 1, the wireless antennas 180 of FIG. 1, or both. Thetransmitter 440 may include the transmitter 118 of FIG. 1. The receiver446 may also be coupled to the wireless antennas 442. For example, thereceiver 446 may include the receiver 178 of FIG. 1.

In a particular embodiment, the processor 410, the display controller426, the memory 432, the CODEC 434, the baseband processors 480, thecamera interface 496, the receiver 446, the transmitter 440, or acombination thereof are included in a system-in-package orsystem-on-chip device 422. In a particular embodiment, an input device430 and the power supply 444 are coupled to the system-on-chip device422. Moreover, in a particular embodiment, as illustrated in FIG. 4, thedisplay device 428, the input device 430, the speaker 436, themicrophone 438, the wireless antennas 442, video camera 498, and thepower supply 444 are external to the system-on-chip device 422. In aparticular embodiment, one or more of the display device 428, the inputdevice 430, the speaker 436, the microphone 438, the wireless antenna442, the video camera 498, and the power supply 444 may be coupled to acomponent of the system-on-chip device 422, such as an interface or acontroller.

In conjunction with one or more of the described embodiments, anapparatus is disclosed that includes means for generating a frame. Themeans for generating the frame may include the processor 108, the packetcreation/encoding module 114, the baseband processor 116 of FIG. 1, theprocessor 410, the encoder 452, the baseband processors 480 of FIG. 4,one or more other devices or circuits configured to generate a frame, orany combination thereof.

The apparatus may also include means for transmitting the frame via asub-1 GHz wireless network at a start time based at least in part on ashort inter-frame spacing (SIFS) time of 160 microseconds. The means fortransmitting the frame may include the baseband processor 116, thetransmitter 118, the wireless antenna 120 of FIG. 1, the basebandprocessors 480, the transmitter 440, the wireless antenna 442 of FIG. 4,one or more other devices or circuits configured to transmit a frame viathe sub-1 GHz wireless network, or any combination thereof.

One or more of the disclosed embodiments may be implemented in a systemor an apparatus, such as the device 400, that may include acommunications device, a fixed location data unit, a mobile locationdata unit, a mobile phone, a cellular phone, a satellite phone, acomputer, a tablet, a portable computer, or a desktop computer.Additionally, the device 400 may include a set top box, an entertainmentunit, a navigation device, a personal digital assistant (PDA), amonitor, a computer monitor, a television, a tuner, a radio, a satelliteradio, a music player, a digital music player, a portable music player,a video player, a digital video player, a digital video disc (DVD)player, a portable digital video player, any other device that stores orretrieves data or computer instructions, or a combination thereof. Asanother illustrative, non-limiting example, the system or the apparatusmay include remote units, such as mobile phones, hand-held personalcommunication systems (PCS) units, portable data units such as personaldata assistants, global positioning system (GPS) enabled devices,navigation devices, fixed location data units such as meter readingequipment, or any other device that stores or retrieves data or computerinstructions, or any combination thereof.

Although one or more of FIGS. 1-4 may illustrate systems, apparatuses,and/or methods according to the teachings of the disclosure, thedisclosure is not limited to these illustrated systems, apparatuses,and/or methods. Embodiments of the disclosure may be suitably employedin any device that includes integrated circuitry including a processorand a memory.

Those of skill would further appreciate that the various illustrativelogical blocks, configurations, modules, circuits, and algorithm stepsdescribed in connection with the embodiments disclosed herein may beimplemented as electronic hardware, computer software executed by aprocessor, or a combination thereof. Various illustrative components,blocks, configurations, modules, circuits, and steps have been describedabove generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or processor executableinstructions depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions are not beinterpreted as causing a departure from the scope of the presentdisclosure.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in random access memory (RAM), flashmemory, read-only memory (ROM), programmable read-only memory (PROM),erasable programmable read-only memory (EPROM), electrically erasableprogrammable read-only memory (EEPROM), registers, hard disk, aremovable disk, a compact disc read-only memory (CD-ROM), or any otherform of non-transient storage medium known in the art. An illustrativestorage medium is coupled to the processor such that the processor canread information from, and write information to, the storage medium. Inthe alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in anapplication-specific integrated circuit (ASIC). The ASIC may reside in acomputing device or a user terminal. In the alternative, the processorand the storage medium may reside as discrete components in a computingdevice or user terminal.

The previous description of the disclosed embodiments is provided toenable a person skilled in the art to make or use the disclosedembodiments. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the principles defined hereinmay be applied to other embodiments without departing from the scope ofthe disclosure. Thus, the present disclosure is not intended to belimited to the embodiments shown herein but is to be accorded the widestscope possible consistent with the principles and novel features asdefined by the following claims.

What is claimed is:
 1. An apparatus comprising a transmitter configuredto transmit a frame, via a sub-1 gigahertz (GHz) wireless network, at astart time based at least in part on a short inter-frame spacing (SIFS)time of 160 microseconds.
 2. The apparatus of claim 1, wherein the starttime is further based at least in part on an air propagation time of 6microseconds.
 3. The apparatus of claim 1, wherein the start time isfurther based at least in part on a clear channel assessment (CCA) timeof 40 microseconds.
 4. The apparatus of claim 1, wherein the start timeis further based at least in part on an air propagation time of 6microseconds and on a clear channel assessment (CCA) time of 40microseconds.
 5. The apparatus of claim 1, wherein the transmitter iscompliant with an institute of electrical and electronics engineers(IEEE) 802.11ah standard.
 6. A non-transitory computer-readable storagedevice storing instructions that, when executed by a processor, causethe processor to initiate transmission, via a sub-1 gigahertz (GHz)wireless network, of a frame at a start time based on a shortinter-frame spacing (SIFS) time, wherein the SIFS time is 160microseconds.
 7. The non-transitory computer-readable storage device ofclaim 6, wherein the start time is further based at least in part on anair propagation time of 6 microseconds.
 8. The non-transitorycomputer-readable storage device of claim 6, wherein the start time isfurther based at least in part on a clear channel assessment (CCA) timeof 40 microseconds.
 9. The non-transitory computer-readable storagedevice of claim 6, wherein the start time is further based at least inpart on a clear channel assessment (CCA) time of 40 microseconds and onan air propagation time of 6 microseconds.
 10. A non-transitorycomputer-readable storage device storing instructions that, whenexecuted by a processor, cause the processor to initiate transmit, via asub-1 gigahertz (GHz) wireless network, of a frame at a start time basedon a clear channel assessment (CCA) time, wherein the CCA time is 40microseconds.
 11. The non-transitory computer-readable storage device ofclaim 10, wherein the start time is further based on a short inter-framespacing (SIFS) time, wherein the SIFS time is 160 microseconds.
 12. Thenon-transitory computer-readable storage device of claim 10, wherein thestart time is further based on an air propagation time of 6microseconds.
 13. The non-transitory computer-readable storage device ofclaim 10, wherein the start time is further based on an air propagationtime of 6 microseconds and on a short inter-frame spacing (SIFS) time,wherein the SIFS time is 160 microseconds.
 14. A method comprisingtransmitting, from a station, a frame via a sub-1 gigahertz (GHz)wireless network, wherein the frame is transmitted at a start time basedat least in part on a clear channel assessment (CCA) time of 40microseconds.
 15. The method of claim 14, wherein the start time isfurther based at least in part on an air propagation time of 6microseconds.
 16. The method of claim 14, wherein the start time isfurther based at least in part on a short inter-frame spacing (SIFS)time of 160 microseconds.
 17. The method of claim 14, wherein the starttime is further based at least in part on a short inter-frame spacing(SIFS) time of 160 microseconds and on an air propagation time of 6microseconds.
 18. An apparatus comprising: means for generating a frame;and means for transmitting the frame, via a sub-1 gigahertz (GHz)wireless network, at a start time based at least in part on a shortinter-frame spacing (SIFS) time of 160 microseconds.
 19. The apparatusof claim 18, wherein the means for generating the frame includes aprocessor.
 20. The apparatus of claim 18, wherein the means fortransmitting the frame includes a transmitter.